"Marvel's Agents of SHIELD" is going big for its thirteenth episode. The above promo claims that the third act of episode 13 could change the entire series forever, which is a big statement to live up to.

The team is heading undercover in "TRACKS," and the episode features the much-touted Stan Lee cameo. He is someone the team meets while on a train pretending to be couples they are not (Simmons as Coulson's pretend daughter? Amazing).

The train mission is an attempt to track down the Clairvoyant. According to SpoilerTV, "Coulson and his team will be hot on the trail of the Clairvoyant. The team will be boarding a mystery train that, 'seems to be headed for certain death.'"

David Conrad will return in "TRACKS" as villain Ian Quinn, who revealed in episode 12 "Seed" that he is connected to the Clairvoyant. "Agents of SHIELD" returns Feb. 4 at 8 p.m. ET/PT on ABC.